Partial joint resurfacing implant, instrumentation, and method

ABSTRACT

A method of repairing an articular cartilage defect with the partial joint resurfacing implant includes surgically creating an opening in the articular cartilage defect site. The method also includes obtaining a partial resurfacing implant which is implanted into the opening. The partial resurfacing implant includes a top articulating portion, an implant fixation portion, and a locking mechanism. The implant fixation portion including an upper segment coupled to the top articulating portion and a bone interfacing segment configured to facilitate insertion into the articular cartilage defect site. The method further includes the bone interfacing segment being inserted into the opening with the top articulating portion and adjacent articular cartilage being positioned to each other to facilitate motion and load transfer over the defect site. Another method of repairing an articular cartilage defect with a partial joint resurfacing implant and a partial joint resurfacing implant are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part application of U.S.application Ser. No. 12/919,607 filed Sep. 10, 2010, which is a nationalstage filing under section 371 of International Application No.PCT/US2009/034826 filed on Feb. 23, 2009 and published in English as WO2009/108591 on Sep. 3, 2009 and claims priority to U.S. ProvisionalApplication No. 61/032,141 filed Feb. 28, 2008, the entire disclosure ofthese applications being hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to surgical devices for use inpartial resurfacing of damaged or diseased articular cartilage of thejoints and to surgical methods using such devices.

BACKGROUND OF THE INVENTION

Articular cartilage, or hyaline type cartilage, is a unique tissueproviding a smooth, lubricious, hydrophilic, load bearing covering onthe ends of bones in diarthroidal joints, in particular the knee, hip,shoulder, to name a few. This tissue is susceptible to damage ordeterioration caused by excessive loading resulting in inflammation,pain, swelling, and joint dysfunction. As a result many methods havebeen developed to clinically treat patients when cartilage degenerationoccurs.

Articular cartilage, or hyaline type cartilage, is a unique tissueproviding a smooth, lubricious, hydrophilic, load bearing covering onthe ends of bones in diarthroidal joints, in particular the knee, hip,shoulder, to name a few. This tissue is susceptible to damage ordeterioration caused by excessive loading resulting in inflammation,pain, swelling, and joint dysfunction. As a result many methods havebeen developed to clinically treat articular cartilage defects.

For smaller cartilage defects surgical techniques have been used tostimulate an intrinsic repair process. These include drilling, abrasionand microfracture of the subchondral bone which induces bleedingresulting in the formation of a new fibrocartilage covering.Unfortunately the biomechanical properties of this tissue is notequivalent to the original hyaline cartilage, and over time the repairtissue is prone to wear, many times resulting in osteoarthritis.

Alternatively, an osteo-articular transfer system (OATS) procedure maybe done, especially as the defect size increases. This techniqueinvolves coring a plug of cartilage and subchondral bone from a nonweight bearing area of the bone and implanting it to a prepared hole inthe defect area. One or multiple plugs can be used to fill the defectarea. This procedure is technically difficult as the coredbone/cartilage plugs must be accurately placed to create the newcontiguous articulating surface. Leaving the surface of the plugs toohigh or low can significantly compromise the surgical outcome. Due tothe multiple drilling locations and angles needed, this procedure istypically done with an open surgical technique followed by a lengthyrehabilitation schedule.

Autologus chondrocyte implantation is a transfer type system wherecartilage cells are harvested in one surgical procedure, expanded in alaboratory, and then injected into the prepared defect site in a secondsurgery. While clinical outcomes are reported to be similar to the abovedescribed techniques this procedure is extremely expensive, requires twosurgeries (one of which is a challenging open procedure), and similarlong rehabilitation schedule.

Other biological attempts have been made to treat larger cartilagedefects with tissue engineered bioabsorbable scaffold systems.Unfortunately they have not shown clinical outcomes advantageous to theabove described techniques.

For many larger defects in the knee the only option available is totreat these defects nonoperatively in an endeavor to control symptomsuntil a unicompartmental knee replacement (UKR) or total kneereplacement (TKR) is accomplished. With these devices both articulatingbone ends are removed and replaced with metal and an ultrahigh molecularweight polyethylene insert (with or without a metal backing) is placedbetween the two metallic pieces. In a UKR both bone ends of the medialor lateral half of the knee are replaced whereas with a TKR both halves(and patella) are replaced. These prosthetic devices require aninvasive, technically demanding implantation procedure and a long,involved, and painful rehabilitation period. Further, these devices areoften larger than the defective tissue that needs to be replaced, sohealthy bone and cartilage are sacrificed to accommodate the implants.Albeit that modern UKR and TKR devices are much improved from earlyhinged knee prostheses, there is still a loss of joint kinematics asthis normal tissue is removed. Additionally, the lifetime of TKRs islimited by a variety of implant and patient-related factors resulting inmany patients outliving their primary prosthetic device, thus requiringa more difficult revision TKR surgery. To avoid this eventual revisionsurgery many younger patients will endure the pain and limited use thesedefects cause in order to put off the TKR procedure as long as possible.It should be noted that the same events occur in the hip and shoulderjoints as well.

Implants constructed using measurements obtained from a defect have alsobeen used. The installed implant thus attempts to closely match theshape of the defective area and articulate directly with the opposingnative cartilage surface. This device has operative advantages overtraditional knee prostheses; however, the opposing articular cartilageis prone to damage due to the large differences in material propertiesand is further exacerbated by any contour mismatching.

Similarly, metals, usually cobalt-chromium or titanium alloys, have beenused for the surface of hip hemiarthroplasties. These prosthetic devicesreplace only the femoral side of the hip joint and articulate againstthe facing cartilage of the acetabulum. These metal implants haveexhibited adverse effects on the cartilage against which they articulatecausing erosion of the facing cartilage in several clinical studies.Thus, merely matching the anatomical shape of the cartilage that isresurfaced is not enough to prevent damage of the facing cartilage by ametallic counterface.

Several researchers have tried using lower modulus polymeric materials,such as high density or ultra high molecular weight polyethylene(UHMWPE), for the surface of hemiarthroplasty implants on the theorythat a material with mechanical properties more closely matched to thoseof cartilage would cause less cartilage damage. These implants alsocaused erosion of the facing cartilage in vivo likely due to a mismatchin surface chemistry properties, (i.e. UHMWPE is hydrophobic andcartilage is hydrophilic). Thus, lower modulus implants alone are notenough to prevent damage of the facing cartilage.

Accordingly there is a need for an improved cartilage replacement systemthat would be effective in restoring a smooth, lubricious, andhydrophilic load bearing surface, with a modulus less than traditionalmetals, that can be easily implanted with minimal normal tissue removal,and requires a less involved rehabilitation schedule ultimatelyrestoring joint kinematics while avoiding damage to the opposingcartilage surface.

SUMMARY OF THE INVENTION

Advancement of the state of surgical repair of damaged or diseasedarticular cartilage of joints is desirable. The present inventionsatisfies the need for improvements to implants and correspondingsurgical instruments used to insert such implants in patients who haveeither diseased or damaged articular cartilage by providing a partialresurfacing implant and instrument system that allows the operatingsurgeon to insert, with accuracy, an implant that maximizes defectcoverage while minimizing host bone and cartilage removal.

The present invention provides in one aspect, a surgical method forrepairing an articular cartilage defect site. The method generallyincludes the step of surgically creating an opening in the articularcartilage defect site. The method may include the step of using apartial resurfacing implant in the defect site. The implant includes atop articulating portion and supporting plate. The supporting plategenerally includes a top surface and a bottom surface. The top surfaceof the supporting plate is attached in some manner to the toparticulating portion with the bottom surface of the supporting platebeing constructed to assist in the insertion of the implant into thearticular cartilage defect site. The method may also include the step ofimplanting the partial resurfacing implant into the defect site opening.Usually, when upon inserting the implant into the defect site, the toparticulating portion and adjacent articular cartilage may be positionedtangential or adjacent to each other which allows for unrestrictedmotion over the defect site while allowing for load transfer to occurthrough the implant to the underlying bone.

The present invention provides in another aspect, a surgical method forrepairing an articular cartilage defect site. The method generallyincludes the step of measuring the size of the articular cartilagedefect site. The method may include the step of aligning a drill guideover the articular cartilage defect site. The method may also includethe step of inserting a pilot drill bit into the drill guide and usingthe pilot drill bit to form at least one pilot hole in the articularcartilage defect site. The at least one pilot hole may be orientedsubstantially normal to the articular cartilage defect site. Once thepilot drill bit is secured to the bone the drill guide may be removed.The method may include the steps of enlarging the at least one pilothole to accommodate a partial resurfacing implant. The method mayfurther include the step of inserting a trial implant into the articularcartilage defect site to confirm the sizing and final positioning of thepartial resurfacing implant. When the correct size trial implant isinserted into the articular cartilage defect site, the size of the trialimplant may then be used to select the partial resurfacing implant. Themethod may also include the step of inserting the partial resurfacingimplant into the articular cartilage defect site. Usually, wheninserting the implant into the defect site, a top portion of the partialresurfacing implant and adjacent articular cartilage may be positionedtangential or adjacent to each other to facilitate motion over thedefect site while allowing for load transfer to occur through theimplant to the underlying bone.

The present invention provides in yet another aspect, an implant forrepairing an articular cartilage defect site. The implant includes a toparticulating portion with an articulating surface and an engagementsurface. The implant fixation portion includes an upper segment and atleast one bone interfacing segment. The upper segment of the implantfixation portion is coupled to the top articulating portion. The atleast one bone interfacing segment of the implant fixation system isconfigured to facilitate insertion into the articular cartilage defectsite. The implant also includes a locking mechanism. The lockingmechanism includes at least two perpendicular protrusions with taperededges on the engagement surface of the top articulating portion and atleast two channels on the upper segment of the implant fixation portion.The at least two channels of the implant fixation portion engage the atleast two protrusions of the top articulating portion to secure the toparticulating portion to the implant fixation portion.

Further, additional features, benefits and advantages of the presentinvention will become apparent from the drawings and descriptionscontained therein. Other embodiments and aspects of the invention aredescribed in detail herein and are considered a part of the claimedinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other objects, features andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a perspective view of a distal condyle of a human femur with acartilage defect, in accordance with an aspect of the present invention;

FIG. 2 is a perspective side view of one embodiment of a cartilageresurfacing implant, in accordance with an aspect of the presentinvention;

FIG. 3 is a perspective side view of a second embodiment of a cartilageresurfacing implant with a single implant fixation portion, inaccordance with an aspect of the present invention;

FIG. 4 is a perspective side view of the second embodiment of acartilage resurfacing implant of FIG. 3 with multiple implant fixationportions, in accordance with an aspect of the present invention;

FIG. 5 is a distal view of one embodiment of multiple cartilageresurfacing implants positioned adjacent to each other, in accordancewith an aspect of the present invention;

FIG. 6 is a perspective view of one embodiment of an anatomical drillguide, in accordance with an aspect of the present invention;

FIG. 7 is a perspective view of one embodiment of a pronged anatomicaldrill guide, in accordance with an aspect of the present invention;

FIG. 8 is a perspective view of one embodiment of a multi-axisanatomical drill guide, in accordance with an aspect of the presentinvention;

FIG. 9 is a side view of one embodiment of an anatomical drill guidepositioned on the distal aspect of a femoral condyle, in accordance withan aspect of the present invention;

FIG. 10 is a side sectional view of a cartilage cutting instrument, inaccordance with an aspect of the present invention;

FIG. 11 is an enlarged side sectional view of the distal end of thecartilage cutting instrument of FIG. 10 positioned adjacent to thefemoral condyle, in accordance with an aspect of the present invention;

FIG. 12 is a sectional side view of a prepared defect site at the distalaspect of the femoral condyle, in accordance with an aspect of thepresent invention;

FIG. 13 is a perspective view of a trial implant before insertion into aprepared defect site, in accordance with an aspect of the presentinvention;

FIG. 14 is a perspective view of an implant insertion instrument, inaccordance with an aspect of the present invention;

FIG. 15 is a perspective view of the resurfacing implant of FIG. 2seated within the prepared defect side in the distal aspect of thefemoral condyle, in accordance with an aspect of the present invention;

FIG. 16 is a top view of the cartilage resurfacing implant of FIG. 4, inaccordance with an aspect of the present invention;

FIG. 17 is a perspective view of the distal aspect of a femur with anattached dual hole drill guide, in accordance with an aspect of thepresent invention;

FIG. 18 is a perspective view of the distal aspect of a femur with dualpilot drills positioned within the drill guide of FIG. 15, in accordancewith an aspect of the present invention;

FIG. 19 is a perspective view of the distal aspect of a femur with dualpilot drills positioned within the drill guide of FIG. 15, in accordancewith an aspect of the present invention;

FIG. 20 is a perspective view of the distal aspect of a femur with oneof the dual pilot drills remaining following removal of the second pilotdrill, in accordance with an aspect of the present invention;

FIG. 21 is a perspective view of the distal aspect of a femur with acutting cannula assembly placed over the single pilot drill, inaccordance with an aspect of the present invention;

FIG. 22 is a perspective view of an inner support member being removedfrom the cutting cannula of FIG. 21, in accordance with an aspect of thepresent invention;

FIG. 23 is a perspective view of a cannulated reamer being placed over asingle pilot drill, in accordance with an aspect of the presentinvention;

FIG. 24 is a perspective view of the distal femur being reamed with thecannulated reamer of FIG. 23, in accordance with an aspect of thepresent invention;

FIG. 25 is a perspective view of the re-insertion of a second pilotdrill into the posterior hole and placement of a cutting tube guide, inaccordance with an aspect of the present invention;

FIG. 26 is a perspective view of the cutting cannula inserted over thesecond pilot drill and abutting cutting tube guide, in accordance withan aspect of the present invention;

FIG. 27 is a perspective view of an inner support member being removedfrom the cutting cannula of FIG. 26, in accordance with an aspect of thepresent invention;

FIG. 28 is a perspective view of the cannulated reamer being placed overthe second pilot drill, in accordance with an aspect of the presentinvention;

FIG. 29 is a perspective view of the cannulated reamer removing bonefrom the distal femur, in accordance with an aspect of the presentinvention;

FIG. 30 is a perspective view of the prepared defect site in the distalfemur, in accordance with an aspect of the present invention;

FIG. 31 is a superior view of a third embodiment of a cartilagereplacement implant, in accordance with an aspect of the presentinvention;

FIG. 32 is a perspective view of the prepared defect site in the distalfemur following the removal of the cartilage flaps, in accordance withan aspect of the present invention;

FIG. 33 is a perspective view of the insertion of a trial sizinginstrument inserted into the prepared defect site of FIG. 32, inaccordance with an aspect of the present invention;

FIG. 34 is a perspective view of the insertion of the cartilagereplacement implant of FIG. 4 prior to final implantation into thedistal femur, in accordance with an aspect of the present invention;

FIG. 35 is a perspective view of the insertion of a trial-drill guidefor the cartilage resurfacing implant of FIG. 3, in accordance with anaspect of the present invention;

FIG. 36A is a perspective view of the prepare defect site after theremoval of the trial-drill guide of FIG. 35, in accordance with anaspect of the present invention;

FIG. 36B is a perspective view of the insertion of the cartilagereplacement implant of FIG. 3 prior to final implantation into thedistal femur, in accordance with an aspect of the present invention;

FIG. 37 is a perspective view of another embodiment cutting cannulaincluding a depth collar, in accordance with an aspect of the presentinvention;

FIG. 38 is a perspective view of the distal aspect of a femur with atrial sizing instrument placed over the defect site, in accordance withan aspect of the present invention;

FIG. 39 is a perspective view of the distal aspect of a femur with adepth probe inserted into the defect site, in accordance with an aspectof the present invention;

FIG. 40 is a perspective view of the distal aspect of a femur with anattached drill guide, in accordance with an aspect of the presentinvention;

FIG. 41 is a perspective view of the distal aspect of a femur with apilot drill being inserted into the drill guide of FIG. 40, inaccordance with an aspect of the present invention;

FIG. 42 is a perspective view of the distal aspect of a femur with dualpilot drills being inserted into an alternative drill guide, inaccordance with an aspect of the present invention;

FIG. 43 is a perspective view of the distal aspect of a femur with aguide tube inserted onto the pilot drill and a cutting cannula beinginserted onto the guide tube, in accordance with an aspect of thepresent invention;

FIG. 44 is a perspective view of the distal aspect of a femur with aguide tube being removed from a reamer depth tube, in accordance with anaspect of the present invention;

FIG. 45A is a perspective view of the distal aspect of a femur with acannulated bone reamer being inserted into a reamer depth tube, inaccordance with an aspect of the present invention;

FIG. 45B is a partial view of the tip of the reamer depth tube of FIGS.44 and 45A, in accordance with an aspect of the present invention;

FIG. 46 is a perspective view of the distal aspect of a femur with adrill bit inserted into a prepared defect site, in accordance with anaspect of the present invention;

FIG. 47 is a perspective view of the distal aspect of a femur showinganother prepared defect site, in accordance with an aspect of thepresent invention;

FIG. 48 is a perspective view of the distal aspect of a femur with atrial being inserted over the drill bit, in accordance with an aspect ofthe present invention;

FIG. 49 is a perspective view of the distal aspect of a femur withanother embodiment trial being inserted into the prepared defect site,in accordance with an aspect of the present invention;

FIG. 50 is a perspective view of the distal aspect of a femur with animplant being inserted into a prepared defect site, in accordance withan aspect of the present invention;

FIG. 51 is a perspective view of the distal aspect of a femur with analternative embodiment implant being inserted into a prepared defectsite, in accordance with an aspect of the present invention;

FIG. 52 is a perspective view of the distal aspect of a femur with theimplant of FIG. 50 inserted into a prepared defect site, in accordancewith an aspect of the present invention;

FIG. 53 is a perspective view of the distal aspect of a femur with theimplant of FIG. 51 inserted into a prepared defect site, in accordancewith an aspect of the present invention;

FIG. 54 is an alternative embodiment of a cartilage resurfacing implant,in accordance with an aspect of the present invention;

FIG. 55 is an isometric top lateral view of an implant fixation portionof the cartilage resurfacing implant of FIG. 54, in accordance with anaspect of the present invention;

FIG. 56 is a lateral view of the implant fixation portion of FIG. 55, inaccordance with an aspect of the present invention;

FIG. 57 is a top view of the implant fixation portion of FIG. 55, inaccordance with an aspect of the present invention;

FIG. 58 is a bottom view of the implant fixation portion of FIG. 55, inaccordance with an aspect of the present invention;

FIG. 59 is an isometric bottom side view of an bearing portion of thecartilage resurfacing implant of FIG. 54, in accordance with an aspectof the present invention;

FIG. 60 is a side view of the bearing portion of FIG. 59, in accordancewith an aspect of the present invention;

FIG. 61 is a bottom view of the bearing portion of FIG. 59, inaccordance with an aspect of the present invention;

FIG. 62 is a top view of the bearing portion of FIG. 59, in accordancewith an aspect of the present invention;

FIG. 63 is a further alternative embodiment of a cartilage resurfacingimplant, in accordance with an aspect of the present invention;

FIG. 64 is an isometric top lateral view of an implant fixation portionof the cartilage resurfacing implant of FIG. 63, in accordance with anaspect of the present invention;

FIG. 65 is a lateral view of the implant fixation portion of FIG. 64, inaccordance with an aspect of the present invention;

FIG. 66 is an anterior view of the implant fixation portion of FIG. 64,in accordance with an aspect of the present invention;

FIG. 67 is an isometric bottom side view of a bearing portion of thecartilage resurfacing implant of FIG. 63, in accordance with an aspectof the present invention;

FIG. 68 is a lateral view of the bearing portion of FIG. 67, inaccordance with an aspect of the present invention;

FIG. 69 is an anterior view of the bearing portion of FIG. 67, inaccordance with an aspect of the present invention.

DETAILED DESCRIPTION FOR CARRYING OUT THE INVENTION

For the purposes of promoting an understanding of the principles of thepartial joint resurfacing implant, corresponding surgical instrumentsand surgical method for inserting the resurfacing implant, referencewill now be made to the embodiments, or examples, illustrated in thedrawings and specific language will be used to describe these. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any alterations and further modificationsin the described embodiments, and any further applications of theprinciples of the invention as described herein are contemplated aswould normally occur to one skilled in the art to which themulti-functional surgical instrument invention relates.

In this detailed description and the following claims, the wordsproximal, distal, anterior, posterior, medial, lateral, superior andinferior are defined by their standard usage for indicating a particularpart of a bone, prosthesis or surgical instrument according to therelative disposition of the surgical instrument or directional terms ofreference. For example, “proximal” means the portion of an implant orinstrument positioned nearest the torso, while “distal” indicates thepart of the implant or instrument farthest from the torso. As fordirectional terms, “anterior” is a direction towards the front side ofthe body, “posterior” means a direction towards the back side of thebody, “medial” means towards the midline of the body, “lateral” is adirection towards the sides or away from the midline of the body,“superior” means a direction above and “inferior” means a directionbelow another object or structure.

As used herein, the terms “partial joint resurfacing implant,”“surfacing implant” and “implant” may be used interchangeably as theyessentially describe the same type of implantable device.

Referring to FIG. 1, cartilage defects 29 in the knee, and morespecifically within the femoral condyle 5 a and other joints, occur as aresult of wear and/or mechanical overloading. They occur in varyingsizes and shapes and tend to progress to larger defects if leftuntreated. To reduce or eliminate the pain caused by these defects andto decrease or eliminate the progression of the joint deterioration, thedamaged cartilage with a portion of underlying bone is removed andreplaced with a device providing a new articulating surface and ananchor into the bone.

Referring to FIG. 2, a generally cylindrical implant 30 b of the presentinvention is shown for example purposes only. The top articulatingportion 30 is made from a material that has a lower modulus ofelasticity then traditional metal implants. In this embodiment, toparticulating portion 30 consists of a polymeric smooth, lubricious, andhydrophilic top surface 30 a fabricated from a polysaccharide-treatedthermoplastic polymer material capable of withstanding in vivo loading.This articulating surface material is more fully described in patentapplication Ser. No. 10/283,760 that is herein incorporated byreference. It should be noted that other biocompatible materials may beused to fabricate top articulating portion 30, that include, but are notlimited to: polysaccharide treated thermoplastic polymers includingpolysaccharides such as hyaluronic acid, chitosan, thermoplasticpolymers such as UHMWPE and other aliphatic polymers like polypropylene,polybutylene, polyethylene-butylene rubber. Also other thermoplasticpolymers such as polyurethanes, polysiloxanes, polyesters, arecontemplated for use. Additional other materials to fabricate toparticulating portion 30 may include polyesters such as PET (polyethyleneterephthalate); perfluorinated hydrocarbons [e.g. teflon]; acrylates[e.g. PMMA (polymethyl methacrylate), polyacrylonitrile,polyacrylomide]; polyamides (e.g. nylon); polycarbonate; epoxy resins;PEEK (polyether ether ketone); ceramics; polysiloxanes (e.g. siliconeresins); metals (e.g. cobalt chrome, titanium and titanium alloys,stainless steel); and hydrogels (e.g. polyvinyl alcohol).

The implant fixation portion 31 of the implant can be constructed ofmetal, polymer, composite or other biocompatible resorbable ornon-resorbable material including, but not limited to, Co—Cr, Ti Alloy,PEEK, UHMWPE or alternatively, entirely from the same material thatmakes up top articulating portion 30.

As shown in FIG. 2, implant 30 b further includes supporting plate 32that has a locking mechanism 33 to securely couple top articulatingportion 30.

The bone interfacing portion of implant fixation portion 31 that extendsfrom supporting plate 32 can be treated or contains features to permitbony ingrowth from the bone bed in which it is implanted. It iscontemplated that implant fixation portion 31 may include a lower stem34 portion containing fixation barbs 35, threads or fins (not shown) tolock implant 30 b into bone. Although not shown, other bone fixationmembers that project from the undersurface of supporting plate 32 arecontemplated and may include tapered stems, straight pegs or a pluralityof pegs. It is also contemplated that implant fixation portion 31 andthe bottom surface of supporting plate 32 could also have a coating orfinish to assist with bone integration, such as HA, TCP or BMP coating,titanium plasma spray, grit blasting, or any other operation thatroughens the surface of the structure. It is understood that theconstruct of implant 30 b as shown in FIG. 2 will minimize the amount ofresected bone which is advantageous for reducing trauma to the remaininghealthy surrounding bone, reducing healing time, and will permit laterremoval without compromising total joint arthroplasty efficacy at thattime. It is further understood by one skilled in the art that implant 30b may be constructed without implant fixation portion 31. It iscontemplated that for such a construct the bottom surface of supportingplate 32 may be coated or finished using the above-named techniques toenhance or assist with bone integration. An embodiment constructedwithout implant fixation portion 31 may be used in various clinicalsituations when a projecting structure is deemed unnecessary.

Top articulating portion 30 of implant 30 b is commonly fabricated usingdirect compression molding techniques to overmold supporting plate 32resulting in a final construct where top articulating portion 30 issecurely adhered to supporting plate 32 via locking mechanism 33.

As described previously, top portion 30 is attached to supporting plate32 via locking mechanism 33 which for example purposes is configured asan undercut dovetail locking arrangement. The angle of the two verticalwalls of the dovetail locking arrangement are generally less than 90degrees, which provides resistance against top articulating portion 30from dislodging superiorly. The nature of the dovetail feature may alsoprevent top articulating portion 30 from rotating relative to thesupporting plate 32. Additionally, locking mechanism 33 may include twodovetail cuts perpendicular to each other, resulting in a cross-shapedarrangement if viewed from a superior perspective. Having multipledirectional cuts helps to ensure that there is no translational orsliding movement of top articulating portion 30 relative to supportingplate 32. Alternative modes of fixing top articulating portion 30 tosupporting plate 32 may also include a snap-fit mechanism, an adhesivematerial or an alternative locking channel.

The bottom aspect of implant 30 b is generally a one-piece constructthat is made up of two different constructs, supporting plate 32 thatholds and supports top articulating portion 30, and implant fixationportion 31 that functions to provide stability and fixation within thehost bone. Supporting plate 32 includes a generally flat bottom surfaceto which implant fixation portion 31 is integrally connected. The topsurface of supporting plate 32 may also be generally flat as well, notwithstanding locking mechanism 33 that is disposed thereon. Implantfixation portion 31 includes a generally cylindrical lower stem 34 partthat includes a proximal cylindrical section and a distal bone fixationsection that includes multiple tapered barbs 35 projecting away from thecentral axis of lower stem 34. Due to the nature of the barb design asshown in FIG. 2, rotation is also prevented post implantation in thebone. The various numbers of barbs 35 that may be employed will rangefrom two to six depending upon their shape and size and quality of boneseen during implantation. The bottom tip 38 of implant fixation portion31 is generally tapered to allow for ease of insertion into the pilothole during the surgical procedure.

Top surface 30 a of implant 30 b can be molded or machined with variousradii to create a contour that closely matches the curvature of theadjacent normal articulating cartilage surface of the subject joint whenimplanted. Alternatively, top surface 30 a may be made substantiallyplanar to avoid being proud relative to the adjacent normal jointsurface and assist in reducing the likelihood of damaging the opposingarticular cartilage surface. Additionally, the peripheral edge of toparticulating portion 30 may have a generous radius 36 around the entirecircumference. This helps to ensure that there are no transitional edgesthat could potential wear down opposing cartilage over time. It alsomakes a smooth transition from the adjacent normal cartilage surface toimplant 30 b. In the event radius 36 or top articulating portion 30 isabsent, the user may trim or cut the surrounding edge during theimplantation procedure to ensure a seamless transition and matchinggeometry between implant 30 b and the surrounding native cartilage.

As shown in FIG. 5 for example purposes only, multiple implants 30 bhave been aligned serially to provide coverage over a wide cartilagedefect that a single implant would not be able to cover. For thispurpose, implant 30 b may be interlocked or joined in some manner toensure bone fixation and continuity of the multiple respective toparticulating portions.

Referring to FIGS. 3, 4, and 16, implant 40 b can be provided in variouscross-sectional geometries or circumferential shapes, including but notlimited to, elliptical, rectangular, oval, oblong and also includefeatures like scallops or flat edges that allow for the placing ofmultiple implants in close proximity to each other to more closely matchand fill the host cartilage defect shape.

An example of alternative shape of implant 40 b includes an oblongconfiguration with a single implant fixation portion as seen in FIGS. 3and 16. The oblong, or “racetrack” shaped implant 40 b is configuredsuch that it might more closely match cartilage defects that are longer,yet narrower, than just a circular defect. Such an implant is similar toimplant 30 b in that it has two components, a top articulating portion40, and a supporting plate 42. Supporting plate 42 may further include acentralized implant fixation portion 41 that has a lower stem 44 partand fixation barbs 45 that extend away from the distal aspect of lowerstem 44. Implant 40 b shown in FIG. 3 has a single implant fixationportion 41 although multiple implant portions 41 are contemplated likethe embodiment shown in FIG. 4.

Similar to implant 30 b, implant 40 b will utilize a locking mechanismsimilar to the previously described dovetail undercut (not shown), thatconnects top articulating portion 40 to supporting plate 42. Toparticulating portion 40 could also be attached to supporting plate 42via a snap-fit mechanism or adhesive material. Similar to implant 30 b,the articulating surface curvature of the implant 40 b is such that itmatches the curvature of the adjacent native cartilage on the femur. Ina normal femur, there are usually two different curvature geometries—onein the anterior-posterior (AP) direction, and one in the medial-lateral(ML) direction, implant 40 b could have a different radius of curvaturein the AP direction as compared to the ML direction in order toaccommodate the natural shape of the native femur. Because of this,implant 40 b has the potential to better fit the geometry of the femurbecause of the dual directional radiuses as opposed to onlyuni-directional radius as use for implant 30 b.

The present invention also discloses a surgical method for the insertionof implant 30 b into the distal femoral condyle.

The first step is typically to assess the size of the defect. Thesurgeon will measure the size of the cartilage defect and cartilagethickness. The size and thickness is used to determine the appropriateimplant size. The thickness measurement is used to determine thedrilling depth of the surface preparation drills and reamers.

Referring to FIG. 6, an anatomical drill guide 4 a is shown. In order toensure that the first hole drilled is normal to the native articulatingcartilage surface, the surgical method utilizes a drill guide thatreferences the geometry of the host articulating cartilage surface.Guide 4 a will reference a femoral condyle in the knee. However, guide 4a could also be designed to reference the geometry of other anatomy inthe knee, hip, shoulder, foot (e.g., great toe), ankle, hand, wrist,spine, etc. The premise would be the same for each anatomic position inthat guide 4 a, whose geometry matches the surface geometry of thenative articulating cartilage surface, is able to pilot the guide holeso that it is drilled normal to the surface.

Typically, a joint will have two or more radius of curvatures—one willbe in the Anterior/Posterior plane (AP curve), and the other will be inthe Medial/Lateral plane (ML curve). Guide 4 a can be marked so that theuser can place guide 4 a in the correct orientation with respect to thearticulating cartilage surface. The typical geometry of the anatomy willbe used to construct under surface 1, 2 of guide 4 a so that it matchesthe cartilage/bone surface. Therefore, guide 4 a will have a curve inthe AP plane, and ML plane, which will allow guide 4 a to sit flush on afemoral condyle. If needed, various sized drill guides can beconstructed to accommodate variations in anatomical size and shape.Further, in some instances the diseased articulating cartilage surfacemight have only one radius of curvature, such as the femoral head in thehip and humeral head in the shoulder, where the shape is more sphericalin nature. In this instance, drill guide 4 a would be shapedappropriately to match either of the AP and ML curves with each beingequal.

In another instance, the diseased articulating surface may be flat ornearly flat, such as areas of the trochlear groove. In this instance,the AP and ML “curves” would be flat planes with infinite radii. Drillguide 4 a underlying surfaces would need to replicate the planararrangement to ensure the pilot hole is drilled normal to the flatsurface.

Further, drill guide 4 a contains a geometrical section 4 which allowsthe user to easily manipulate and place the anatomical drill guide.Drill guide 4 a also has a thru hole 3 that is sized appropriately for apilot drill bit 11 (see FIG. 11) to be inserted. As a result of drillguide 4 a being normal to the articular surface, the pilot drill bit 11(see FIG. 11) will also be normal to the articular surface.

Referring to FIG. 7, an anatomical drill guide 4 b is shown in analternative embodiment. Drill guide 4 b has three prongs 22 that areequal in length. By having three prongs with equal lengths, one can findthe normal axis on a curved surface by ensuring three points of contact.Prongs 22 are all smooth and rounded on the end 24 to prevent scuffingor damaging of the cartilage during placement of guide 4 b.Additionally, guide 4 b can also have a center hole 23 which serves as aguide for the pilot drill bit. Center hole 23 will ensure that the pilotdrill bit 11 (see FIG. 11) will be placed normal to the surface of thediseased articular cartilage.

Referring to FIG. 8, a multi-axis anatomical drill guide 4 c isdepicted. In many instances, a defect site will not be circular inshape, and, thus, a standard circular implant will not fully cover theaffected area. As a result, multiple implants may be needed to beimplanted into the defect site. In order to address such a presentedclinical situation where standard circular implants are not adequate,multiple holes could be drilled normal to the articular cartilagesurface. The present invention describes drill guide 4 c that allows theuser to drill multiple (e.g. three) holes. Drill guide 4 c willreference the AP radius of curvature 25 as well as the ML radius ofcurvature 28 such that it will lay flush against the diseased articularcartilage surface. Multiple holes 27 are present in drill guide 4 cwhich are each normal to the curves at their respective locations. Holes27 are used as guides for inserting a pilot drill 11 (not shown), whichwill ensure that all three holes 27 are drilled normal to the articularcartilage surface. Additionally, drill guide 4 c has a cannulatedgeometrical piece 26 attached that allows for manipulation and placementof the drill guide 4 c.

Referring to FIG. 9, it is shown for the next step of the surgicalmethod that the placement of guide 4 a must be so that the interface 5of drill guide 4 a and the femoral condyle 5 a is such that guide 4 a isflush with the articular cartilage surface 5 b.

Once guide 4 a is in place, the surgical method provides for using anappropriate sized drill bit to create the hole for accommodating implant30 b. The drill bit is used until the etch line on the drill bit linesup with the back surface of drill guide 4 a. This allows a set depth tobe drilled.

A further step is to keep drill guide 4 a in place, remove the drill bitand insert a separate insertion rod into the pilot hole that was made inthe bone. An alternate to this step would be to unchuck the drill bitfrom the drill and just remove the drill guide leaving the drill bitintact. As a result, one could now use the drill bit instead of aseparate insertion rod. Following this step, drill guide 4 a may beremoved by sliding it over the insertion rod (or drill bit, ifalternative method is used).

Referring to FIG. 10, a cartilage cutting instrument assembly 21 isshown. Instrument 21 comprises a sharp cutting edge 6 that is used tosever the cartilage. By severing the cartilage, a nice clean cut iscreated at the defect site, which enables better cartilage interfacewith implant 30 b. The cutting tube 10 a is attached to an ergonomichandle 7 to allow the user to easily grasp and manipulate theinstrument. Another component of instrument 21 is the intermediatesupport tube 8, which is attached to another ergonomic handle 10 toallow for the user to remove support tube 8 from instrument 21 whenneeded. Intermediate support tube 8 is cannulated 9 such that it fitsover the pilot drill bit 11 (see FIG. 11) or alternatively, an insertionrod (see FIG. 11) that was inserted following pilot hole generation.

The next step of the surgical method may include sliding instrument 21over insertion rod (or pilot drill bit) until sharp cutting edge 6touches articular surface 5 b. The user will gently twist and pushinstrument 21 until the layer of cartilage is cut and the cutting edge 6is touching the subchondral bone.

As seen in FIG. 11, instrument 21 is positioned adjacent to femoralcondyle articular cartilage surface 5 b prior to cutting the cartilage12. Intermediate support tube 8 fits over pilot drill bit 11 that wasplaced using anatomical drill guide 4 a. Cutting edge 6 is twisted,rotated, pushed or struck as required to cut and sever cartilage 12.Cutting edge 6 is not intended to significantly cut into the underlyingsubchondral bone. Once cartilage 12 is severed, intermediate supporttube 8 is removed. This leaves only pilot drill bit 11 and cutting tube10 a in place.

Because intermediate support tube 8 is removed, a next step for thesurgical method would be to insert a cannulated reamer (not shown) thatfits into and through cutting tube 10 a and over pilot drill bit 11.This is done to ensure that the larger hole is also oriented normal tothe femoral surface. An etch mark on the reamer will reference the backof handle 10 (see FIG. 10) or, alternatively, an adjustable stop (notshown) could be used on the reamer to set the depth to be reamed whichcorresponds to the height of implant 30 b. Additionally, cutting tube 10a acts as a protection barrier to keep the adjacent outer cartilagewhich is not to be removed from making contact, and thus being damaged,with the reamer. This will likely ensure that the clean-cut surface fromthe cartilage remains intact, which will assist in creating andmaintaining a favorable interface between the native cartilage andimplant 30 b.

The next step of the surgical method will usually be to remove drill bit11 (or insertion rod) and cutting tube 10 a. The site is now prepared toreceive implant 30 b. Alternatively, the cutting tube 10 a can be leftin place to provide a barrier to prevent cartilage edge damage and fluidentrapment in the defect site.

Referring to FIG. 12, the resultant stepped implant preparation hole 14a in femoral condyle 12 is shown after the preceding drilling andreaming operations are completed. The smaller hole 13 is a result ofpilot drill bit 11 (see FIG. 11). The larger hole 14 is a result ofusing a cannulated reamer to ream to the correct depth. Smaller hole 13houses lower stem 34 of implant 30 b and more generally, implantfixation portion 31, while larger hole 14 houses the recessed toparticulating portion 30.

The surgical method further provides for the insertion ofappropriate-sized trial implants. This will ensure that the proper fitand orientation is achieved prior to inserting implant 30 b. As shown inFIG. 13, trial component 16 a is used to verify a proper fit betweenimplant 30 b and stepped implant preparation hole 14 a. Trial component16 a contains a cylindrical piece 15 that has the same diameter (orslightly smaller) and height as the proposed implant 30 b (see FIG. 2).In the preferred embodiment, the trial component 16 a can have a stem 16that is attached to the cylindrical piece 15 to allow for easiermanipulation of the trial. By inserting trial 16 a into prepared hole 14a, one can test the fit of implant 30 b and stepped implant preparationhole 14 a prior to the insertion of implant 30 b. Specifically,important feedback given by trial component 16 a is whether implant 30 bwill be proud, recessed, or oblique relative to the native articulatingcartilage surface 5 b which could all potentially adversely affect thepost-operative functioning of implant 30 b. If after inserting thecylindrical piece 15 it is found that implant 30 b may be proud, one caneither ream deeper into the bone or select an implant with a smallerheight if available. Conversely, if cylindrical piece 15 is found to berecessed, one can select an implant with a larger or thicker height.

Referring to FIG. 14, an implant insertion instrument 17 a is shown.Instrument 17 a contains a soft (e.g. silicone-coated) tip 17 that isplaced on a sturdy or rigid tube 21 that is preferably, but notnecessarily metallic. Tip 17 a can also be manufactured from any othersoft or pliant material that will not damage top articulating portion 30or top surface 30 a upon insertion. It serves as a cushion and protectsimplant 30 b from any harmful impaction forces. In this embodiment,instrument 17 a has a back portion 20 that can be interfaced with asuction hose. This suction keeps implant 30 b in close proximity tosilicone tip 17 until proper positioning is achieved. The suction can beeasily controlled by the user via a small communication hole 19 that canbe covered and uncovered as necessary with one's hand or finger tocontrol the suction. Additionally, the handle portion 18 can be tappedon to ensure implant 30 b is seated flush in the bone.

Referring to FIG. 15, implant 30 b is seated in femoral condyle 5 areplacing cartilage defect 29. Special care is taken to make sure toline up implant fixation portion 31 in smaller hole 13 and to ensurethat implant 30 b is flush with the inner shoulder of large hole 14, andarticular cartilage surface 5 b.

Referring collectively to FIGS. 17-36B, the present invention alsodiscloses a further surgical method for inserting an oblong or“racetrack” shaped implant 40 b (see FIG. 16) that includes either asingle implant fixation portion 41 (see FIG. 3) or dual implant fixationportions (see FIG. 4).

As discussed previously, many defects found in the knee are not perfectcircles and tend to be longer in the Anterior-Posterior (AP) plane thanthe Medial-Lateral (ML) plane. Therefore, having an implant that moreclosely matches the shape of defects typically seen will be advantageousin that the defect can be more easily covered than with acircular-shaped implant similar to implant 30 b.

The surgical method for inserting implant 40 b includes, as seen in FIG.17, the step of using an anatomic drill guide 100 whose curvatureclosely matches that of the femur 50, and placing it on the femoralcondyle over the defect. Instead of a single pilot hole (as done whenpreparing defect site for implant 30 b), there are two pilot holesdrilled. These holes represent the two axes of implant 40 b (see FIG.16) and the corresponding two implant fixation portions.

The surgical method provides further as shown in FIG. 18, the step ofinserting two pilot drills 101 into each hole on drill guide 100 anddrilling to the proper depth. The depth can be set via a mark on drillbits 101 that line up with the back of drill guide 100. Once both pilotdrills 101 are inserted, drill guide 100 is removed as shown in FIG. 19.

The surgical method may include the step of removing one of the pilotdrills 101 and leaving the posterior hole 51 exposed (see FIG. 20). Acutting cannula assembly 102, 103 is then slid down pilot drill 101 (seeFIG. 21). Twisting motion to assembly 102, 103 will cause the sharp tipof the assembly to sever the targeted diseased cartilage.

Once the cartilage is severed, the surgical method will provide for thestep of removing the inner support piece 103 while keeping the outercannula 102 and pilot drill 101 in place (see FIG. 22). A cannulatedbone reamer 104 is then placed over pilot drill 101 (see FIG. 23) andthe bone is reamed to a set depth (see FIG. 24). Again, the depth of thebone cut can be determined via a mark or collar on reamer 104 thatreferences the back of cutting cannula 102.

The surgical method provides further for the step of cutting thecartilage for the second axis as determined by the second drill bit.Specifically, using a similar method to cut the cartilage as for thefirst axis described above, cutting cannula 102 and pilot drill 101 fromthe first axis are removed, pilot drill 101 is reinserted into posteriorhole 51 that replicates the second axis. Also, a cutting tube guide 200is inserted into the adjacent the hole that has been previously drilled(see FIG. 25). Guide 200 has a cutout such that the outer diameter ofcutting tube 102 fits snuggly into it. The purpose of guide 200 is toensure that when cutting the cartilage along the second axis, cuttingcannula 102 is forced along a certain path. Without guide 200, there isa possibility that cutting cannula 102 will slide slightly inwards(anteriorly) towards the first pilot hole, thus making the defectslightly smaller than desired. Using the same method as the first axis,cutting cannula 102 is then slid down pilot drill 101 and into guide 200allowing for the cartilage to be is severed (see FIG. 26).

The surgical method may then include the step of reaming the bone outfrom the second axis. This is accomplished by removing inner-supportpiece 103 while keeping cutting cannula tube 102 in place (see FIG. 27).Cannulated bone reamer 104 is then placed over pilot drill 101 (see FIG.28), and the bone is then reamed to a set depth as shown in FIG. 29.Again, the depth of the bone cut can be determined via a mark or collaron reamer 104 that references the back of cutting cannula 102.

Following the drilling over the second axis, the resulting shape of theprepared defect site resembles a “figure 8” as shown in FIG. 30. It iscontemplated that an alternative implant could have an outerconfiguration of a “figure 8” 50 b (see FIG. 31), such that it fitswithout having to do additional defect site preparation. However,typically the shape of the implant is more of a “racetrack” or oblong asseen in FIGS. 3, 4 and 16, such that it gets maximum coverage.Therefore, in order to accommodate the oblong shape, the flaps ofcartilage are removed via an osteotome, drill, burr, or other sharpcutting instrument resulting in the final defect site shape as seen inFIG. 32.

The surgical method may have the further step of inserting a trial 300to assess how the fit of the implant will be (see FIG. 33). Trial 300geometry matches the geometry of the actual implant. This will allow theuser to visualize how the implant fits into the defect site. If theimplant is too proud, recessed, or not perpendicular, trial 300 willenable the user to correct the sizing prior to inserting the actualimplant. A preferred position of the implant 30 b, 40 b may, forexample, be slightly recess from the surrounding cartilaginous surface.

The surgical method will generally then provide for the step ofinserting the implant into the defect site. The two implant fixationportions 41 of implant 40 b are lined up with the two pilot holes (seeFIG. 34). Implant 40 b is then tapped into place until it is flush withthe surrounding cartilaginous surface.

In the event implant 40 b has only a single implant fixation portion 41(see FIG. 3), the surgical method steps outlined above would be thesame. However, since the implant has one implant fixation portion 41that is located at the center of the oval, another pilot hole must becreated. In order to do this, one would also use trial 300 as a drillguide to drill the center hole (see FIG. 35). Once the center hole 54 iscreated, the defect now has a total of three holes (see FIG. 36A).Single implant fixation portion 41 implant 40 b is then lined up withthird, center hole 54 (see FIG. 36B) and is tapped into place.

Referring now to FIG. 37, an alternative embodiment cutting cannula 202is shown. The cutting cannula 202 may be, for example, used in place ofthe outer cannula 102, discussed in greater detail above. The cuttingcannula 202 includes a body 204 and a collar 206. The body 204 mayinclude a plurality of cutting depth dimension designations 208 whichcorrespond to a plurality of slots 210 in a first end of the body 204.The slots 210 may have various depths which correspond to the depthdrilled by the cannulated bone reamer 436. The depths of the slots 210correspond with the depth dimension designations 208 on the body 204.The slots 210 may, for example, increase in ½ mm increments, asillustrated by the designations 208, although other dimension incrementsare also contemplated. The depth of the slots 210 may, for example,range from about 0 mm to about 8 mm, and more preferably, for example,range from approximately 0 mm to approximately 4 mm. The collar 206 mayinclude a pin 212 on an inner surface of the collar 206 and a stopsurface 214 on the top of the collar 206. When the physician decideswhat depth the bone should be reamed, the physician may insert thecollar 206 onto the body 204 sliding the pin 212 into the slot 210 whichdesignates the desired depth. The pin 212 mates with the slots 210 ofthe body 204 to secure the collar 206 in the desired position to achievea desired depth. As a cannulated bone reamer 436 is inserted into thecutting cannula 202 a stop mechanism, such as a shoulder, on thecannulated bone reamer 436 will engage the stop surface 214 of thecollar 206 to prevent the cannulated bone reamer 436 from going deeperinto the bone than the selected depth. The cutting cannula 202 may alsobe used in the method discussed below with reference to FIGS. 38-54.

Referring now to FIGS. 38-54, the present invention discloses anothersurgical method for inserting an implant 400 into the distal femoralcondyle. The surgical method of inserting implant 400 includes,assessing the size of the defect. The surgeon will measure the size ofthe cartilage defect and may measure the cartilage thickness. The sizeof the cartilage defect may be measured by placing the appropriate sizetrials 410 over the defect until one completely covers the defect. Thecartilage thickness may be measured using a depth probe 420 which may beinserted into the articular cartilage around the edge of the defect siteuntil the probe 420 touches the subchondral bone. The size and thicknessmay be used to assist in determining the appropriate implant size, forexample, implant 400 may be selected. The thickness measurement may alsobe used in determining the drilling depth of the surface preparationdrills and reamers.

The surgical method provides further for the step of using an anatomicdrill guide 422 whose curvature closely matches that of the femur 50,and placing it on the femoral condyle over the defect, as illustrated inFIG. 40. The drill guide 422 includes a handle with a cannulated holesection 424 which allows the user to easily manipulate and place theanatomical drill guide 422 on the defect. The drill guide 422 may alsoinclude a thru hole 426 that is sized to allow a pilot drill bit 450 tobe inserted. The pilot drill bit 450 is drilled or tapped to the properdepth and the proper depth may be set using a mark on the drill bit 450that lines up with the top of the handle of the drill guide 422. Asillustrated in FIG. 42, if the defect requires an oblong implant, suchas implant 500 shown in FIG. 52, the anatomic drill guide 428 with twothru holes 426 may be used. If anatomic drill guide 428 is used, twopilot drill bits 450, 452 will be inserted into the two thru holes 426.

Once the pilot drill bit 450 is inserted into the femur, the drill guide422 may be removed and a guide tube 430 may be placed over the pilotdrill bit 450, as shown in FIG. 43. Next the cutting cannula 432 may beplaced over the guide tube 430. The surgeon may then twist or turn thecutting cannula 432 to cut the targeted diseased cartilage away from thedistal femur. The cutting cannula 432 may then be removed leaving theguide tube 430 over the pilot drill bit 450.

The surgical method may include the step of inserting a reamer depthtube 434 over the guide tube 430. Once the reamer depth tube 434 isseated properly on the cartilage, the guide tube 430 may be removed, asshown in FIG. 44. While the guide tube 430 is being removed the reamerdepth tube 434 and the pilot drill 450 should remain in place. Acannulated bone reamer 436 is then placed over pilot drill 450 and thebone is reamed to a set depth, as shown in FIG. 45A. The depth of thebone cut may be determined via a mark or collar on the reamer 436 thatreferences to the back of the reamer depth tube 434. As seen in FIG. 46,the reamer 436 and reamer depth tube 434 may then be removed leaving thedrill bit 450 in the center of the circular prepared defect site 438.Referring now to FIG. 45B, a partial view of one embodiment of the tipof the reamer depth tube 434 is shown. The reamer depth tube 434 mayinclude a body 440 with a sharp edge 442 extending away from the bodyand a shoulder 444 between the body 440 and the sharp edge 442. As thereamer depth tube 434 is inserted into the patient's cartilage the sharpedge 442 cuts the cartilage until the shoulder 444 of the reamer depthtube 434 mates with the top of the cartilage. The shoulder 444 providesa visual stop for the physician as the reamer depth tube 434 isinserted.

If the defect required an oblong implant, as shown in FIG. 52, or“figure 8” implant and the anatomic drill guide 428, shown in FIG. 42,was used, then the first pilot drill bit 450 would be removed from thefirst drill hole 454 after the reamer 436 and reamer depth tube 434 wereremoved. The second pilot drill bit may then be inserted into the seconddrill hole 452 and a similar method as discussed with reference tocutting the cartilage with the drill bit 450 in the first drill hole 454will be used. A guide tube 430 may be placed over the pilot drill bit450 and the cutting cannula 432 may be placed over the guide tube 430.The physician using, for example, a rotating or twisting motion willrotate the cutting cannula 432 to cut the diseased cartilage and thenthe cutting cannula 432 may be removed. A reamer depth tube 434 may thenbe inserted over the guide tube 430 with the pilot drill bit still inplace. The guide tube 430 may then be removed leaving the drill bit 450in place. The cannulated bone reamer 436 is inserted over the pilotdrill 450 and the physician reams the bone to the desired depth, thereamer 436 may then be removed from the drill bit 450 and the reamerdepth tube 434 is extracted. Following the drilling over the secondpilot drill bit inserted in the second drill hole 452, the resultingshape of the prepared defect site resembles a “figure 8,” as shown inFIG. 47. If the shape of the implant is oblong, the flaps of cartilagemay be removed via an osteotome, drill, burr, or other sharp cuttinginstrument resulting in the final defect site shape 458, as seen in FIG.49.

The surgical method may have the further step of inserting a trial 460to assess the fit and orientation of the implant, as shown in FIG. 48.If the implant 500 is oblong, a trial 502 will be inserted to assess thefit and orientation of the implant 500, as seen in FIG. 49. The trials460 and 502 will have geometries which match the outer geometry of theactual implants 400, 500, respectively. The implant 400 may be, forexample, the type described in greater detail below with reference toFIGS. 54-62. If the implant is not aligned with the surroundingarticular surface or not perpendicular, trials 460, 502 will enable theuser to correct the sizing prior to inserting the actual implant. Ifafter inserting the trials 460, 502 it is found that the implants 400,500 protrude, one can either ream deeper into the bone or select animplant with a thinner construct if available. The method may alsoinclude the step of using the trial 460 to enlarge the circular prepareddefect site 438 to accommodate the partial resurfacing implant 400. Thetrial 460 may include cutting edges to enable the trial 460 to reamdeeper into the bone by, for example, rotating the trial 460 until aproper depth is achieved. When the trial 460 is used to ream deeper intothe bone the physician may visually confirm when enough bone has beenreamed for the implant 400 to be in the desired position when inserted.Conversely, if the trials 460, 502 are found to be recessed to deepwithin the bone, one can select an implant with a larger or thickerconstruct. In addition, if after inserting the implant 400 it is foundthat the normal axis is not aligned to the articulating surface, thepilot drill 450 may be removed and a trial 460 with cutting edges may berotated to reestablish the normal axis by visual confirmation.

The surgical method will then generally provide for the step ofinserting the implant into the defect site, as shown in FIG. 50. Theimplant 400 will have an implant fixation portion 402 with aninterfacing segment 480 that may, for example be a post, stem, rod, orother protruding structure. The interfacing segment 480 is lined up withthe pilot hole 404. Implant 400 is then tapped into place until the topsurface is, for example, flush or substantially even with thesurrounding cartilaginous surface as illustrated in FIG. 52. In apreferred embodiment the implant 400 may, for example, be tapped untilslightly recessed from the surrounding cartilaginous surface. Theimplant 400 may be, for example, slightly recessed by approximately a ¼mm to approximately 2.5 mm and more preferably recessed about a ½ mm toabout 2 mm from the surrounding cartilaginous surface. The implant 500may have two interfacing segments 504, 506 that will be lined up withthe pilot holes 452, 454, respectively. Alternatively, the implant 500may only include one implant fixation portion, as described in greaterdetail below with reference to implant 550 in FIGS. 63-69. The implant500 is then tapped into place until the top is, for example,substantially even or adjacent with the surrounding cartilaginoussurface as illustrated in FIG. 53. In a preferred embodiment the implant500 may, for example, be slightly recessed from the surroundingcartilaginous surface. The implant 500 may be, for example, slightlyrecessed by approximately ½ mm to approximately 2 mm from thesurrounding cartilaginous surface. Once the implant 400 or 500 is inplace, the surgeon may reduce the joint and close the patient'sincision.

Referring now to FIGS. 54-62, the implant 400 is shown in greaterdetail. The implant 400 includes an implant fixation portion 402 and atop articulating portion 406. The implant fixation portion 402, as shownin FIGS. 55-58, may be of the type described above with reference to theimplant fixation portion 31 of FIG. 2, although implant fixation portion402 has an alternative bone interfacing segment 480. The implantfixation portion 402 includes an upper segment 470 with a boneinterfacing segment 480 extending down from the under surface. The uppersegment 470 of the implant fixation portion 402 includes a supportingplate 472 with a locking mechanism 474 extending away from thesupporting plate 472. The locking mechanism 474 may include at least twosubstantially perpendicular channels 476 and a plurality of lockingprotrusions 478. In the depicted embodiment there are four protrusions478 created by the intersection of the two substantially perpendicularchannels 476. The channels 476 may have lateral walls that are angledless than 90 degrees to create a female portion of a dovetail lockingarrangement. Alternatively, the lateral walls of the channels 476 may besubstantially perpendicular to each other. The locking mechanism 474 maybe used to securely couple the implant fixation portion 402 and the toparticulating portion 406 together.

As seen in FIGS. 55-58, the bone interfacing segment 480 of the implantfixation portion 402 may include a stem 488 which has an insertion end486 which may be tapered for assisting in insertion into the patient'sbone. The implant fixation portion 402 may also include a plurality offixation fins 482 extending out from the central axis of the stem 488and the fixation fins 482 may be tapered from the supporting plate 472to the insertion end 486 of the stem 488 for locking the implant 400into the bone. The fins 482 may also contain at least one notch 484 nearthe supporting plate 472 or in the superior portion of the boneinterfacing segment 480 allowing for bone ingrowth or cement securementafter implantation. The fins 482 may assist in preventing rotation postimplantation in the bone. The number of fins 482 on the bone interfacingsegment 480 may range between two and six depending on the size andshape of the fins, as well as, the quality of the bone surrounding theimplant 400. Additional bone fixation members and/or coatings orfinishes may also be used on the bone interfacing segment 480, asdescribed above with reference to FIG. 2. It is also contemplated thatthe bone interfacing segment 480 may be, for example, a flange, rod,post, or other protruding structure. The implant fixation portion 402may be made of a biocompatible material as described above withreference to the implant fixation portion 31 of FIG. 2.

The top articulating portion 406 may be fabricated from the same type ofmaterial as described above with reference to the top articulatingportion 30 of FIG. 2. The top articulating portion 406, shown in FIGS.59-62, may include an articulating surface 490 and an engagement surface492. The articulating surface 490 may be substantially adjacent to thearticulating cartilage surface that surrounds the implant 400. Thearticulating surface 490 may be substantially planar or contoured tomatch the curvature of the normal articulating cartilage surface of thedistal femur surrounding the implant 400. The top articulating portion406 may come in a variety of thicknesses to enable the surgeon to selectthe top articulating portion 406 that best matches the height andcurvature of the surrounding natural articulating cartilage surface. Theengagement surface 492 may include a locking mechanism 494 which engagesthe locking mechanism 474 of the upper segment 470 of the implantfixation portion 402 to secure the top articulating portion 406 to theimplant fixation portion 402. The locking mechanism 494 of the toparticulating portion 406 may include at least two substantiallyperpendicular protrusions 496 and a plurality of openings 498. In thedepicted embodiment as seen in FIG. 59, there are four openings 498created by the intersection of the two substantially perpendicularprotrusions 496. The protrusions 496 may have angled lateral walls whichtaper from the inferior end of the engagement surface 492 creating themale portion of a dovetail locking arrangement. Alternative protrusion492 shapes are also contemplated.

The protrusions 496 of the top articulating portion 406 may be insertedinto the channels 476 of the implant fixation portion 402 to secure thetop articulating portion 406 to the implant fixation portion 402. Oncethe protrusions 496 are inserted into the channels 476, the protrusions478 of the locking mechanism 474 mate with the openings 498 of thelocking mechanism 494. Where the locking mechanisms 474, 494 have adovetail arrangement, the protrusions 496 of the locking mechanism 494may experience resistance from the channels 476 of the locking mechanism474 preventing the top articulating portion 406 from dislodgingsuperiorly from the implant fixation portion 402. The substantiallyperpendicular channels 476 and protrusions 496 may also assist inpreventing translational or sliding movement of the top articulatingportion 406 relative to the implant fixation portion 402. The assemblyof the top articulating portion 406 to the implant fixation portion 402may be accomplished, for example, using a molding process.

Referring now to FIGS. 63-69, the implant 550 is shown in greaterdetail. The implant 550 includes an implant fixation portion 552 and atop articulating portion 554. The implant fixation portion 552 may be ofthe type described above with reference to the implant fixation portion41 and supporting plate 42 of FIGS. 3 and 16, although the implantfixation portion 552 has an alternative bone interfacing segment 564.The implant fixation portion 552 includes an upper segment 555 and abone interfacing segment 564 extending away from the under surface ofthe upper segment 555. The bone interfacing segment 564 is of the typedescribed above with reference to bone interfacing segment 480 of FIGS.54-58. The bone interfacing segment 564 has the same or similar elementsas bone interfacing segment 480 including a stem 488 with an insertionend 486, a plurality of fixation fins 482 extending out from the centralaxis of the stem 488, and at least one notch 484 in each of the at leastone fixation fins 482. Although implant 550 includes only one boneinterfacing segment 564, it is contemplated that multiple boneinterfacing segments 564 could be used, such as shown with implant 500in FIG. 51.

The upper segment 555 of the implant fixation portion 552 includes asupporting plate 556 with a locking mechanism 558 extending in asuperior direction out from the supporting plate 556. The supportingplate 556 and locking mechanism 558 are similar to the type describedabove with reference to the supporting plate 472 and locking mechanism474 of FIGS. 54-58, however the supporting plate 556 and lockingmechanism 558 of the implant fixation portion 552 have an oblongconfiguration rather than the cylindrical shape of the implant fixationportion 402 of implant 400. The oblong shape of the supporting plate 556may create substantially perpendicular channels 560 with differentlengths. In the depicted embodiment, the two perpendicular channels 560have different lengths, one channel runs in an anterior-posteriordirection on the locking mechanism 558 and another channel runs in amedial-lateral direction on the locking mechanism 558. It is alsocontemplated that the channels 560 may run diagonally through theintersection of a point in the center of the locking mechanism therebyproviding channels 560 which have equal lengths. In the embodimentdepicted in FIG. 64, the channels 560 run in the anterior-posterior andmedial-lateral directions of the implant fixation portion 552, theprotrusions 562 may be curved or tapered in both directions. The lockingprotrusions 562 of the locking mechanism 558 may be curved or tapered inthe anterior-posterior and medial-lateral directions to correspond tothe curvature of the top articulating portion 554 and maximize thicknessof the top articulating portion 554.

The top articulating portion 554, as shown in FIGS. 67-69, may includean articulating surface 566 and an engagement surface 568. Thearticulating surface 566 may be of the type described above withreference to the top articulating portion 40 of FIGS. 3, 4, and 16. Thecurvature of the articulating surface 566 is shaped to substantiallymatch the curvature of the adjacent native cartilage on the surroundingdistal femoral bone. The top articulating portion 554 may come in avariety of thicknesses to enable the surgeon to select the toparticulating portion 554 that best matches the height and curvature ofthe surrounding articulating cartilage surface. The articulating surface566 of the top articulating portion 554 may have at least two differentcurvature geometries, for example, a first in the anterior-posteriordirection and a second in the medial-lateral direction creating animplant 550 with dual directional radiuses.

The engagement surface 568 may be of the type described above withreference to the engagement surface 492 of FIGS. 59-61 and may include alocking mechanism 576 with at least two substantially perpendicularprotrusions 570, 572 and a plurality of openings 574. The protrusions570, 572 are of the type described above with reference to protrusions496, however, as the implant 550 is oblong the protrusions 570 in theanterior-posterior direction may be longer than the protrusions 572 inthe medial-lateral direction. The lengths of the protrusions 570, 572correspond to the lengths of the channels 560 in the implant fixationportion, thereby enabling the locking mechanism 576 of the toparticulating portion 554 to mate or couple with the locking mechanism558 of the implant fixation portion 552. The protrusions 562 also mayengage the openings 574 when the top articulating portion 554 isinserted onto the implant fixation portion 552.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprise” (andany form of comprise, such as “comprises” and “comprising”), “have” (andany form of have, such as “has”, and “having”), “include” (and any formof include, such as “includes” and “including”), and “contain” (and anyform of contain, such as “contains” and “containing”) are open-endedlinking verbs. As a result, a method or device that “comprises,” “has,”“includes,” or “contains” one or more steps or elements possesses thoseone or more steps or elements, but is not limited to possessing onlythose one or more steps or elements. Likewise, a step of a method or anelement of a device that “comprises,” “has,” “includes,” or “contains”one or more features possesses those one or more features, but is notlimited to possessing only those one or more features. Furthermore, adevice or structure that is configured in a certain way is configured inat least that way, but may also be configured in ways that are notlisted.

While embodiments of the invention have been illustrated and describedin detail in the disclosure, the disclosure is to be considered asillustrative and not restrictive in character. All changes andmodifications that come within the spirit of the invention are to beconsidered within the scope of the disclosure.

What is claimed is:
 1. A method of repairing an articular cartilagedefect site, the method comprising: measuring the size of the articularcartilage defect site; surgically creating an opening in the articularcartilage defect site; obtaining a partial resurfacing implant, theimplant comprising: a top articulating portion, the top articulatingportion including an articulating surface and an engagement surface; animplant fixation portion, the implant fixation portion comprising anupper segment and at least one bone interfacing segment, the uppersegment of the implant fixation portion is coupled to the toparticulating portion and the at least one bone interfacing segment ofthe implant fixation portion is configured to facilitate insertion intothe articular cartilage defect site; and a locking mechanism; andinserting the implant fixation portion into the opening with the toparticulating portion and adjacent articular cartilage being positionedadjacent to each other to facilitate motion and load transfer over thedefect site.
 2. The method of claim 1, wherein the surgically creatingan opening further comprises employing a drill guide to form at leastone pilot hole in the defect site, the at least one pilot hole beingoriented substantially normal to the articular cartilage defect site. 3.The method of claim 1, wherein the surgically creating an openingfurther comprises cutting damaged articular cartilage from the articularcartilage defect site.
 4. The method of claim 1, wherein the surgicallycreating an opening further comprises enlarging the pilot hole toaccommodate the implant.
 5. The method of claim 1, wherein thesurgically creating an opening further comprises reaming the articularcartilage defect site to a height of the implant.
 6. The method of claim1, further comprising the step of inserting a trial implant within thearticular cartilage defect site to confirm the sizing and finalpositioning of the partial resurfacing implant.
 7. The method of claim1, wherein the inserting the implant fixation portion into the openingfurther comprises seating the implant using at least one of an implantinsertion instrument or a portion of a hand into the articular cartilagedefect site.
 8. A method of repairing an articular cartilage defectsite, the method comprising: measuring the size of the articularcartilage defect site; aligning a drill guide over the articularcartilage defect site; inserting a pilot drill bit into the drill guideand using the pilot drill bit to form at least one pilot hole in thearticular cartilage defect site, the at least one pilot hole beingoriented substantially normal to the articular cartilage defect site;removing the drill guide from the pilot drill bit; enlarging the atleast one pilot hole to accommodate a partial resurfacing implant;inserting a trial implant into the articular cartilage defect site toconfirm the sizing and final positioning of the partial resurfacingimplant; selecting the partial resurfacing implant with a proper size;and inserting the partial resurfacing implant into the articularcartilage defect site with a top portion of the partial resurfacingimplant and adjacent articular cartilage being positioned adjacent toeach other to facilitate motion and load transfer over the defect site.9. The method of claim 8, wherein enlarging the pilot hole toaccommodate the implant, comprises: inserting a guide tube over thepilot drill bit; inserting a cutting cannula over the guide tube;rotating the cutting cannula to cut diseased cartilage from thearticular cartilage defect site; removing the cutting cannula from theguide tube; inserting a reamer depth tube over the guide tube; removingthe guide tube from inside the reamer depth tube; inserting a cannulatedbone reamer inside the reamer depth tube; reaming the diseased cartilagefrom the articular cartilage defect site to match a height of thepartial resurfacing implant; and removing the cannulated bone reamer andthe reamer depth tube.
 10. The method of claim 8, wherein the implantingthe partial resurfacing implant into the articular cartilage defect sitefurther comprises inserting the implant into the articular cartilagedefect site.
 11. The method of claim 8, wherein the partial resurfacingimplant comprises: a top articulating portion, the top articulatingportion including an articulating surface and an engagement surface; animplant fixation portion, the implant fixation portion comprising anupper segment and at least one bone interfacing segment, the uppersegment of the implant fixation portion being configured to secure tothe top articulating portion and the at least one bone interfacingsegment of the implant fixation portion being configured to facilitateinsertion into the articular cartilage defect site; and a lockingmechanism comprising: at least two substantially perpendicularprotrusions on the engagement surface of the top articulating portion;and at least two channels on the upper segment of the implant fixationportion for engaging the at least two protrusions of the toparticulating portion to fix the top articulating portion to the implantfixation portion.
 12. An implant for repairing an articular cartilagedefect site, the implant comprising: a top articulating portion, the toparticulating portion including an articulating surface and an engagementsurface; an implant fixation portion, the implant fixation portioncomprising an upper segment and at least one bone interfacing segment,the upper segment of the implant fixation portion is configured tocouple the top articulating portion and the at least one boneinterfacing segment of the implant fixation portion is configured to beinserted into the articular cartilage defect site; and a lockingmechanism comprising: at least two protrusions with tapered edges on theengagement surface of the top articulating portion; and at least twochannels on the upper segment of the implant fixation portion sized forengaging the at least two protrusions of the top articulating portion tolock the top articulating portion to the implant fixation portion. 13.The implant of claim 12, wherein the articulating surface of the toparticulating portion includes a plurality of curvatures.
 14. The implantof claim 13, wherein the plurality of curvatures includes at least oneradius of curvature with the at least one radius of curvature beingselected to approximate a surface contour of the articular cartilagesurrounding the defect site.
 15. The implant of claim 13, wherein theplurality of curvatures includes at least two radii of curvature,wherein a first radius of curvature of the at least two radii ofcurvature is greater than or equal to a second radius of curvature ofthe at least two radii of curvature, with the at least two radii ofcurvature being selected to approximate the surface contour of thearticular cartilage surrounding the defect site.
 16. The implant ofclaim 12, wherein the articulating surface of the top articulatingportion is planar to approximate the surface contour of the articularcartilage surrounding the defect site.
 17. The implant of claim 12,wherein the at least one bone interfacing segment of the implantfixation portion is integrally connected to and extending away from abottom surface of the upper segment of the implant fixation portion. 18.The implant of claim 17, wherein the at least one bone interfacingsegment includes at least two fins projecting away from an outer surfaceof the at least one bone interfacing segment, the at least two fins eachincluding at least one notch in a proximal portion of the at least twofins, the fins being configured to inhibit motion of the implantfollowing implantation in the articular cartilage defect site.
 19. Theimplant of claim 18, wherein the bottom surface of the upper segment ofthe implant fixation portion and the at least one bone interfacingsegment are coated with a material for facilitating bio-ingrowth betweenthe implant and the articular cartilage defect site.
 20. The implant ofclaim 12, wherein the engagement surface and the upper segment of theimplant have a mating surface shape, the mating surface shape being oneof a circle, an oval, a rectangle, an oblong, or a polygonal shape, theshape of the mating surface is configured to fit within the articularcartilage defect site.